Transit of Venus on 2012 June 06: stray light estimation and restoration of Ca-K images of Twin Telescope from Kodaikanal Observatory

K. Prabhu1, K. E. Rangarajan1, B. Ravindra1, K. Sankarasubramanian2,1, R. Selvendran3 and P. Kumaravel3
1Indian Institute of Astrophysics, Bengaluru 560 034, India
2Space Astronomy Group, ISRO Satellite Centre, Bengaluru 560 034, India
3Indian Institute of Astrophysics, Kodaikanal, India
Received: 01 March 2013 | Accepted: 12 September 2013

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Abstract

Observations of the transit of Venus were made from the Kodaikanal Observatory on 2012 June 06 in Ca-K wavelengths. Only half of the event was visible from India. We utilized this unique opportunity to compute the contribution of the scattered light within the Twin Telescope optics at Kodaikanal. The instrumental and atmospheric scattered light are derived from the model point spread function which is a combination of four Gaussians with different widths and weights. The restoration procedure has significantly improved the rms contrast of the images. The rms contrast of the stray light corrected images are almost two fold larger than that those of the uncorrected images. The derived network element sizes matches well with previous observations.

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Keywords : techniques: miscellaneous – atmospheric effects – telescopes – Solar system: general